Light emitting diodes (LED's) are commonly used for many applications, including displays, electronic status identifications, lighting applications, and the like. In electronic applications, LED's are often used as indicators. In a simple application, an LED is commonly used in a wide variety of consumer electronics, where the LED would be illuminated to indicate that power is available to a device, that the device is turned on, that the device is turned off, and the like. LED's may also be used to indicate when data is being transferred by an electronic communication device, such as a modem, an Ethernet switch, a router, and the like. Additionally they may be used in commercial or industrial applications for information displays, indicators, or other reasons. Current trends continue the increase the inclusion of high power LED's in industrial and commercial lighting applications. These LED's are slightly different from LED's used in common consumer applications, where the high power LED's require much better heat dissipation in order to extend their lifespan. Specialized dielectrics have been developed as one resolution to address the heat dissipation requirements, however, this solution is provided at a significantly high cost.
LED's can be used in a wide range of lighting applications, including reading lights, portable flashlights, accent and decorative lighting, traffic signals, and exterior automotive signals, and the like. These and other applications vary widely in terms of color, brightness and luminescence required.
Typically, LED devices comprise a small semiconductor die assembled into a package. The LED semiconductor die is attached to a support substrate, which provides mechanical support and the necessary electrical conduits for providing electrical communication between a printed circuit assembly and the LED. A lens is assembled to the support substrate in an arrangement to disburse the light emitted by the light emitting semiconductor die. When electrical power is provided to the semiconductor die, the die produces light that is dispersed through the lens. Often, it is convenient to mount an LED directly onto a printed circuit board (PC board) both to incorporate the LED in the electronic device, and to provide power to the LED from the PC board circuitry.
LED's also dissipate heat during operation. Without using the proper precautions, they can build up enough heat within the LED to cause a reduction in light output, or ultimately failure of the LED device. It is well known in the LED semiconductor industry that the light output from an LED device decreases with increasing junction temperature, as illustrated in the Luxeon Emitter Technical Datasheet DS25. It is common practice to mount these LED onto PC boards that contain specialized dielectrics providing a suitable thermally conductive heat sink for the purpose of drawing heat away from the die to maintain higher light output, and prevent thermally related device failures. However, at best, these specialized dielectrics conduct at a rate of 3 W/m-K, which is not considered to be very good.
What is desired is an LED heat sink assembly that provides improved thermal management without specialized and costly dielectrics for the LED semiconductor device, resulting in improved light output and at a reduced cost.
Additionally desired is an improved method to assemble the LED heat sink assembly to a printed circuit board without using solder or soldering techniques to make the connection.